1. Field of the Invention
The present invention relates to a double facer in a corrugate machine.
2. Description of the Prior Art
At first, one example of a double facer in a corrugate machine in the prior art will be described with reference to FIGS. 5, 6 and 7. In FIG. 7, reference numeral (026) designates a double facer in a corrugate machine, and this double facer (026) is composed of a heating part (024) and a cooling part (025). Reference numeral (01) designates a single-faced corrugated cardboard sheet or sheets produced by a single facer (not shown) in the preceding step of the process, numeral (02) designates a liner, numeral (03) in FIGS. 5, 7 and 8 designates a blower, numeral (06) designates an air chamber provided in the above-mentioned heating part (024), numeral (05) designates a pressurized air feed pipe extending from the same blower to the air chamber (06), numeral (04) designates pressurized air, numeral (07) designates an upper side canvas belt provided over the aforementioned heating part (024) and the above-mentioned cooling part (025), numeral (08) designates a corrugated cardboard sheet, numeral (010) designates a sheet introducing section, numeral (011) designates a lower side heating box (hot plate section) provided in the above-mentioned heating part (024), and the interior of this heating box (011) is adapted to be heated by steam. In addition, reference numeral (027) in FIG. 7 designates a lower side conveyor belt provided in the cooling part (025), numeral (028) designates press rollers provided in the same cooling roller, numeral (029) designates a gluing machine, numeral (030) designates a preheat roller, and after the liner (02) has passed through the gluing machine (029), it is preheated and conditioned by the preheat roller (03) and fed to the lower side heating box (hot plate section) (011). On the other hand, after the single-faced corrugated cardboard sheet or sheets (01) have passed through the gluing machine (029), they join with the liner (02) at the sheet introducing section (010), and thereafter they come into contact with the upper side canvas belt (07) and are sent to the heating part (024). In other words, the single-faced corrugated cardboard sheets (01) and the liner (02) are held in contact with the upper side canvas belt (07) and the lower side heating box (011) and thus pinched and conveyed thereby through the heating part (024). At this moment, the pressurized air (04) is fed through the route of the blower (03) .fwdarw. the pressurized air fed pipe (05) .fwdarw. the interior of the air chamber (06), further it is fed from the air chamber (06) onto the back side of the canvas belt (07), thereby the single-faced corrugated cardboard sheet (01) and the liner (02) are pressed towards the heating box (011), and crest portions (09) of the corrugations of the single-faced cardboard sheet (01) and the liner (02) are made to stick to each other by paste (031) applied to the crest portions (09) of the corrugations as shown in FIG. 9. Subsequently, they enter the cooling part (025), where they are conveyed by the canvas belt (07) on the upper side and the conveyor belt (027) on the lower side, during this period they are again pressed via the press rollers (028) and the canvas belt (07) and thereby formed into a corrugated cardboard sheet (08), and then the corrugated cardboard sheet (08) is sent to the next step of the process.
In the heretofore known double facer shown in FIGS. 5, 6 and 7, during the period when the single-faced corrugated cardboard sheet (01) is passing through the gap between the air chamber (06) and the heating box (011), the both side edge portions of the single-faced corrugated cardboard sheet (01) directed in its lengthwise direction having a small crush-resistance are crushed by the air pressure applied by the air chamber (06) and the weight of the both side edge portions of the canvas belt (07) directed in its lengthwise direction tend to sag (See portion (A) in FIGS. 8 and 9). Especially, in the case where the size of the corrugated cardboard boxes being manufactured is small and so a single-faced corrugated cardboard sheet having a narrow width has been fed, the above-mentioned tendency is so remarkable that gap clearances are produced between the side walls of the air chamber (06) and the both side edge portions of the canvas belt (07) directed in its lengthwise direction and the pressurized air (04) leaks out through these gap clearances (See FIG. 8), hence the pressing force exerted upon the both side edge portions of the single-faced corrugated cardboard sheet (01) directed in its lengthwise direction at the both side edge portion of the canvas belt (07) is reduced, and therefore, unacceptable products are produced due to the fact that the both side edge portions of the single-faced corrugated cardboard sheet (01) directed in its lengthwise direction and the liner (02) cannot well stick to each other. Furthermore, since the pressurized air (04) leaks out, it was necessary to use a blower (03) having a large capacity, and so, there was a problem that a driving power expense was unfavorably increased.